Gear pumps typically include a housing or plate that holds a set of intermeshing gears. As the gears turn, fluid moves between the gear teeth and the housing and is expelled out the pump due to the intermeshing of the gears. The gears are attached to shafts that run axially from the gear faces, and these shafts must run on one or more bearing surfaces.
Gear pumps find application in a variety of industries. In the case of gear pumps used for polymer extrusion it is important to have the fluid ports as near to the entrance and outlet of the gear “mesh” as possible in order to reduce the amount of time the polymer resides in the pump, and to minimize the total amount of heat added to the polymer by the pump. The housing or plate that contains the gear set includes one or more ports machined into its side. The housing or plate may be substantially wider than the gear set to receive bolts of a flange that attaches to the pump. This extra housing space may accommodate bearings for supporting the gear shafts. Providing discrete shaft bearings allows for better shaft alignment than arrangements in which the shafts are simply mounted in separate plates attached to the gear housing.
Traditionally, where the pump includes a pair of intermeshing gears, two separate bearings have been employed, one for each drive shaft on each side of each gear, resulting in a total of four bearings per pump. The general shape of the traditional gear cavity in the housing is similar to a figure “8”. Each bearing may have a round portion with a flat side. The flats sides of two bearings are then aligned and installed into the pump housing as a pair, with one pair on each side of the gears.
The traditional bearings may also include features used to help remove trapped fluid from the gear mesh. Often such features are machined on the individual bearing pieces as two separate features. Because the bearing assemblies are made up of so many individual bearing pieces, it is easy for these features to be misaligned during manufacturing and installation. Such misalignment can cause the pump to perform in a less than desired manner. Moreover, the large number of pieces used in the bearing assembly, and the importance of the inter-fitting of the bearing pairs in the bearings into the bearing cavity, makes assembly of the pump very difficult.
Thus, there is a need for an improved bearing assembly for pumps in general and gear pumps in particular. Such an improved bearing assembly should be easy to install, and should reduce the total number of individual parts required for assembly. The improved bearing assembly should also include features that will reliably enable trapped fluid to be removed from the gear mesh. There is also a need for an improved arrangement that ensures a desired alignment of the components of a gear pump is obtained as the components of the pump are being assembled.